The present invention relates to a lightwave system for selectively connecting input/output ports by optical paths.
The prior art lightwave systems are disclosed in xe2x80x9cBell Labs Technical Journal, January-March 1999, pp. 220-224xe2x80x9d, for example. The literature discloses an arrangement including a combination of multiplexer/demultiplexer elements and optical switches, an arrangement including a combination of arrayed waveguide diffraction gratings and phase shifters, and an arrangement including variable optical fiber gratings. In these arrangements, an optical path through which an optical signal proceeds is basically selected in accordance with the wavelength by switching elements. The prior art lightwave systems for selectively connecting input/output ports are categorized into two types. In the first type of the lightwave system, wavelength division multiplexed (WDM) optical signals are divided into a plurality of optical signals of different wavelengths, and then the optical signals are sent through an optical path selection element to the different output ports, respectively. In the second type of the lightwave system, a multiport system including 2xc3x972 switching elements in cascade connection is provided where a single switching element is capable of selecting an output path in accordance with the wavelength.
The above-described prior art lightwave systems require that demultiplexing or multiplexing elements for WDM optical signals be provided in anticipation of an increased number of ports, resulting in a high initial cost for the manufacture of a lightwave system.
Another drawback of the prior art lightwave systems lies in the lack of flexibility, that is, the lightwave systems cannot be expanded later to add a variety of functions.
It is an object of the present invention to provide a lightwave system which can selectively connect input/output ports by optical paths with a simple arrangement while affording an excellent expandability.
According to the present invention, a lightwave system comprises an optical signal bus; an input/output interface including a first port, a second port and a third port, an optical signal inputted to the first port being outputted from the second port, an optical signal inputted to the third port being outputted from the first port; an optical tap, through which the optical signal which is outputted from the second port of the input/output interface is sent to the optical signal bus; a variable wavelength filter, through which an optical signal having a designated wavelength is outputted from the optical signal bus, thereby being sent to the third port of the input/output interface; and a controller which designates the wavelength of the optical signal which is to be sent from the optical signal bus through the variable wavelength filter.
According to another aspect of the present invention, a lightwave system comprises a plurality of layers, each of which includes an optical signal bus, an optical tap, through which an optical signal is sent to the optical signal bus, and a variable wavelength filter, through which an optical signal having a designated wavelength is outputted from the optical signal bus; an input/output interface including a first port, a second port and a third port, an optical signal inputted to the first port being outputted from the second port, an optical signal inputted to the third port being outputted from the first port; a wavelength splitter which divides a wavelength division multiplexed optical signal into optical signals having different wavelengths, a wavelength division multiplexed optical signal inputted to the first port of the input/output interface being transmitted through the second port of the input/output interface to the wavelength splitter, the optical signals produced by the wavelength splitter being transmitted through the optical taps to the optical buses, respectively; and an optical multiplexer which multiplexes optical signals to produce a wavelength division multiplexed optical signal, optical signals being transmitted through the variable wavelength filters to the optical multiplexer, a wavelength division multiplexed optical signal produced by the optical multiplexer being sent to the third port of the input/output interface; and a controller which designates the wavelength of the optical signal which is to be sent from the optical signal bus through the variable wavelength filter.
In the lightwave system of the present invention, a number of input/output interfaces, which maybe as many as can be desired, are connected to the optical signal bus. Input/output interfaces connected to the optical signal bus can be augmented by connecting a variable wavelength filter or an optical tap, thus affording an excellent expandability.
In a case where WDM optical signals are divided by the optical splitter to be sent to each optical signal bus layer, the number of wavelengths per optical signal bus layer can be reduced so that the lightwave system can provide a large scale of wavelength channels.
Furthermore, in a case where the star coupler is used with the optical signal bus or where the optical linear bus is used as the optical signal bus, distribution of optical signals is facilitated.